Gluconeogenesis Flashcards
Gluconeogenesis is _______ synthesis of glucose.
De novo
Gluconeogenesis is synthesis of glucose form __________ substrates.
non-carbohydrate
What are some of the non-carbohydrate substrates used in Gluconeogenesis.
Pyruvate
Glycerol from adipose tissue
glucogenic amino acids from muscle protein
Enzymes for Gluconeogenesis are found where?
Only in liver, kidney, and intestinal epithelium
Gluconeogenesis main occurs where?
Cytosol of liver cells
During prolonged starvation what becomes the major glucose producing organs?
kidneys
When glucose is not available what does the brain use for fuel?
ketones
When does gluconeogenesis occur?
Durian fasting, starvation, or intense exercise
Gluconeogenesis is highly ________. (energy requiring)
endergonic
Can humans make glucose from acetyl CoA?
NO
Glucokinase is replaced by which enzyme?
Glucose-6-phosphatase
PFK is replaced by which enzyme?
Fructose-1,6-bisphosphatase
Pyruvate kinase is replaced by which enzyme?
Pyruvate carboxylase and PEP carboxykinase
What is the common substrate for gluconeogenesis?
Lactate/lactic acid
Lactic acid is converted into _______ by which cycle?
pyruvate
Cori cycle
What enzyme is used to convert lactate to pyruvate?
Lactate dehydrogenase
What is the glucogenic amino acid that can convert to pyruvate?
alanine
The Cori cycle comes at a net loss of how many ATP?
4
What does the Cori cycle do?
Prevents lactic acid from building up in the muscles.
The first step of gluconeogenesis occurs where?
mitochondrion
The rest of gluconeogenesis (not 1st step) occurs where?
cytosol
What enzyme converts pyruvate to oxaloacetate? This occurs where?
Pyruvate carboxylase
Mitochondrion (1st step)
What is the essential coenzyme for the 1st reversal step? (pryruvate to oxaloacetate)?
biotin (B7)
A biotin deficiency will cause what to build up resulting in excess production.
lactate
What are allosteric activators of the 1st reversal step in gluconeogenesis?
ATP and Acetyl CoA
What is the second part reversal?
Oxaloacetate to phosphoenolpyruvate
What enzyme is used in the second step?
PEP carboxylase
Where does the second step occur?
cytoplasm
PEP carboxylase is facilitate by what?
Glucagon and cortisol
Is lots of energy needed for step two reversal?
yes
What is the rate limiting step of gluconeogenesis?
Step 3 reversal: fructose-6-phosphate from fructose 1,6-bisphosphate
What is the enzyme for step 3 reversal?
Fructose 1,6- bisphosphatase
What stimulates fructose 1,6-bisphosphase?
ATP and citrate
What inhibits fructose 1,6–bisphosphatase?
AMP and fructose 2,6-bisphosphate
What is the enzyme for step 1 glycolysis reversal?
Glucose-6 phosphatase
What does glucose 6-phosphatase do?
coverts glucose 6-phophate into glucose
Where is glucose 6-phosphatase located?
ER of liver and kidney cells
G6P is ________ as it passes into the ER.
hydrolyzed
Gluconeogenesis is inhibited by ______ and stimulated by _______.
insulin
glucagon
Gluconeogenesis DOES NOT occur in _____ and the ____.
Muscles
brain
Gluconeogenesis is an energy _______ process.
consuming
How many ATP does gluconeogenesis use to produce one glucose molecule?
6
Why is acetyl CoA not used to make glucose?
Requires more energy than using lactate or alanine
If the glucose made is not used immediately, then what happens to it?
Converted and stored as glycogen in liver or skeletal muscle.
